1. Field of the Invention
The present invention relates to a burn-in test with an integrated circuit device, and more particularly to a socket and method for performing a burn-in test with various bare chips which have not yet encapsulated.
2. Description of the Prior Art
In the processing sequence of semiconductor device, It is very necessary for an integrated circuit (hereinbelow referred to as "Ic") chip to test its lifetime and reliability before sending out goods. For the purpose of the test a chip targeted is put into an abnormally loaded condition of high temperature and high voltage. Such a test configuration is called burn-in test.
There is a well-known technology of the burn-in test as shown in FIG. 1 in the prior art in which the status of the chip to be tested is an encapsulated chip packaged with molding compound through a molding process. Burn-in socket shown in FIG. 1 consists of a plurality of socket holes 14 in whitest a plurality of lead pins 12 of assembly 10 are inserted to electrically contact therewith, a plurality of socket pins 16 composed of metal and electrically contacted with the socket hole 14, and body 15 which accomodates the assembly 10 and in which the socket pins are established downward. For the burn-in test, the burn-in socket accommodating the assembly 10 targeted is mounted on a burn-in board (not shown) by the socket pins 16 and then test signal is applied into the IC chip of the assembly 10 in the abnormally extremity condition of higher temperature and voltage than that of a normal operating condition. An IC chip incapable of end during the test gets around to being failed as destruction of gate oxide film and thereby is regarded to as an inferior chip to be abandoned.
However, the configuration of the conventional built-in test just can be adaptable to one assembly which is encapsulated, but not to a bare chip, resulting in the Baste of the cost for packaging such an inferior chip.
In a recently proposed and advanced integrated technology multi-chip module (abbreviated to "MCM"), useful to increase the operating speed, integrating density and size, employing a flip chip in which a plurality of bare chips are mounted on a board by means of face-down bonding method, it is rigorously important to secure sufficient known-good dies (abbreviated to "KGD") those are bare chips tested so that there have been no defects (See PROJECT RETORT of MICROELECTRONICS AND COMPUTER TECHNOLOGY Co., published on October, 1992). The MCM, however, also has a problem incapable of manufacturing the KGDs of low cost because a bare chip without pins as the assembly of FIG. 1 cannot be tested by using the conventional burn-in socket as shown in FIG. 1.
To overcome the limitation is disclosed in U.S. Pat. No. 5,006,792 to provide the flip chip test socket adapter as shown in FIG. 2A for performing the burn-in test in the status of bare chip in which a plurality of solder bumps are formed on its pads. The flip chip of FIG. 2A as the IC chip 22 having solder bumps 24 on its bonding pads are inserted into the test socket adapter as shown in FIG. 2B to be tested in the burn-in mode. The test socket adapter includes the substrate 28 on which the cantilever beams 26 are formed. Also on the substrate 28 the guide bar 25 is established to support the IC chip 22 inserted and to adjust the alignment between the solder bumps and the cantilever beams 26. The substrate 28 is accommodated within the case 20. A plurality of socket leads 23 connected to a test board (not shown) through the case 20 are electrically connected to the cantilever beams 26. The elastic plate 30 is attached under the cover 29 at the top of the case 20 to make the IC chip 22 be well contacted with the cantilever beams 26 by pushing the back side of the IC chip 22 with elastic pressure by itself. However, in the conventional configuration, very expensive equipment is necessary to precisely form the solder bumps on the bonding pads of the IC chip in which the pitch between the bonding pads is very fine as an microscopic dimension, resulting in a KGD of high cost. Moreover, the cantilever beams should be changed to another type corresponding to another IC chip or the position of the bonding bumps and its metal of material is flexible to cause the life time of test socket adapter to be shorten. In addition, the back side of the IC chip is physically damaged due to the elastic plate which pushes the IC chip down to enhance the electrical contact with them.